Sampling devices or "samplers" are commonly used in oil production when custody of the oil changes. They receive or extract a representative sample of the oil being transferred, such as that oil flowing in a pipeline. Subsequent laboratory analysis of the samples taken by the "sampler" reveals the percentages of wax, basic sediment and water in the oil.
Prior devices used for sampling have suffered from various problems. They may consist of valves used to allow the admission and exit of oil through a passageway from the vessel being sampled and this passageway can become clogged with foreign material in the oil including wax. Disassembly of the sampler for cleaning purposes may be necessitated by the deposit of the foreign substance in the passageway.
A further problem associated with prior devices is that whereas sampling is ordinarily taken automatically, it may be desired to manually rotate the valves to obtain a fluid sample. Disassembly of the sampler may again be necessary and, upon reassembly, the timing sequence of the valve operation used in automatic sampling may need readjustment.
Yet a further problem associated with pior samplers relates to the removal of the sampler from the pipeline or vessel containing the fluid to be sampled. Removal of the sampler may be desired for purposes of repair or maintenance and to accomplish the removal, tedious precautions may be necessary when removing the sampler including, in some instances, the necessity for temporarily shutting down the pipeline.
Finally, previous samplers may be designed to operate completely only under certain pressure limits of the fluid in the pipeline. If the pressure is too low, the operation of the sampler is no longer effective. Accordingly, it is desirable for a sampler to operate without regard to the minimum pressure in the pipeline or fluid carrying vessel.